The invention relates to an apparatus for generating a local electron-cyclotron microwave low-pressure plasma at a predetermined location within a processing chamber of the apparatus. With the plasma generated in this way, the surface of an exposed substrate can be etched, modified, coated by a substance or structured.
Such systems or apparatus are highly important in connection with the plasma-based formation of layers or for the treatment of surfaces. The microwave energy is coupled in a pulsed form or continuously. How the microwave energy is supplied depends on the treatment process, or, respectively, the way of supplying the energy to an exposed substrate. A coating process for example magnetron sputtering, vapor deposition, or arc vaporization is supported in that a plasma is projected in front of the substrate to be coated. Furthermore, a substrate or a substrate surface may be modified as follows:
The surface of a substrate or a surface area of a substrate may be oxidized by an oxygen- or inert gas/oxygen plasma, by nitrating the surface or the surface area to a depth of several 100 μm, which can be achieved with a nitrogen or inert gas/nitrogen plasma; by borating the surface of the surface area of the substrate, which can be achieved by a chloro-boride, fluor-boride or inert gas/chloro-fluoride plasma, a boron containing gas plasma or a boron-containing inert gas plasma, but also a combination of the three mentioned possibilities.
WO 96/23318 discloses a plasma reactor for generating and maintaining a plasma in a hollow space resonator. This reactor is used for example in the thin film coating technology. With it, hard material layers, particularly diamond layers can be generated for the material synthesis and powder synthesis processes and nitration and etching in plasma surface treatments. The cross-section of the hollow space resonator becomes smaller in the apex area. The wall of the hollow space resonator is closed in the apex areas to such an extent that an excited field mode has in the area of the cross-section restrictions main maximas whose maximal field strength exceeds the field strength of the neighboring side maximas. In the area of a main maximum is a reaction unit with a substrate which is to be treated, that is, which is to be coated from the gas phase. Process parameters such as gas pressure and coupled-in magnetic energy can be selected to a large extent independently of one another if the position of the plasma is stable without an undesired discharge of the plasma in the side maxima of the field strength distribution in the resonator. The main maxima of the field strength distribution should be higher than the others to such a degree that a plasma discharge occurs only in those areas.
The hollow space resonator of the reactor has such a firm geometry that at least two main maxima occur in the field distribution where a discharge can be initiated. They must have a clearly greater height than the other maxima. Such a resonator geometry is in the complete ellipsoid or two parabolic parts each with an apex, which are coupled by way of a cylindrical intermediate part toward the hollow resonator space. At one of the focal points of the hollow space geometry a microwave is introduced; the plasma is formed at the other focal point which represents the load center. The plasma is generated by beam focusing without magnetic field influence and therefore associated with a rigid resonator geometry or respectively, two of such main maxima, a source and a sink.
It is the object of the present invention to provide a system for generating an electron cyclotron resonance microwave plasma in a vacuum apparatus wherein the location of the plasma can be controlled.